The invention is directed to a process for production of sorbents for uptake of liquids. These sorbents are suitable for taking up any desired liquids; however, they are especially good as pet litter.
The keeping of pets in a largely urbanized environment is increasingly dependent on the use of litter materials. The task of these materials is to absorb the fluids given off by the animals and to suppress or prevent the development of odor if possible. Moreover, they are required to remove moisture from the semisolid, moist animal excrement and excretions, in order to reduce the development of odor. Good litter materials, furthermore, have the property of taking up the excreted or removed fluids by forming a compact clump, which can be removed in a simple and economical way. Therefore, an optimal animal litter has a high absorption capacity.
The products that can be found on the market include organic substances such as straw, sawdust, wood shavings, bark, porous synthetic beads, shredded paper, cellulose fibers, agricultural wastes, polyacrylates, etc. These are used by themselves or in mixtures with inorganic materials. The disadvantage of the organic litter materials is an often unsatisfactory clumping or consistency of the clump, as well as their tendency to bacterial decomposition, especially in conjunction with moisture.
Japanese No. 60,258,101 discloses water dispersable granulates used as pest control agents containing a mixture of bentonite and diatomaceous earth as the carrier, as well as a small quantity of alkaline phosphate. These products are only mixtures of materials. There is no activation of the bentonite.
Japanese No. 58,128,146 discloses a sorbent for volatile inorganic hydrides which are obtained by the impregnation of solid silicate carriers, such as diatomaceous earth, calcium silicate or bentonite, with aqueous solutions of alkalis such as sodium hydroxide, potassium hydroxide or calcium hydroxide. There is no kneading or activation of the sorbent disclosed.
Japanese No. 53,065,283 discloses a method for removing contaminants from exhaust gases by the use of granulates of bentonite, potassium permanganate, sodium hydroxide, cement as a binding agent and, possibly, activated charcoal. The sodium hydroxide is not kneaded with the bentonite nor is it used for its activation.
Japanese No. 52,065,767 discloses a method for the removal of ammonium compounds, in which the ammonium compound is brought into contact with the synthetic aluminum silicate or a clay material, such as bentonite, which has previously been made amorphous. The absorbent after its use is regenerated by a treatment with an alkaline solution, whereupon the bound ammonium ions are replaced by alkaline ions.
U.S. Pat. No. 5,037,412 discloses a sorption pad for body fluid containing a sorbent such as a mixture of citric acid, sodium biocarbonate and zeolite in a casing. Bentonite is not disclosed in this patent.
U.S. Pat. No. 4,641,605 discloses an animal litter which delays the release of ammonia. The litter contains a sorbent, such as bentonite, which is mixed with oxidation agents, such as alkaline persulfates and ammonium persulfate. Neither serves as an activation agent for the product.
U.S. Pat. No. 4,913,835 discloses an agent for the neutralization and solidification of spilled, hazardous alkaline liquids comprised of a mixture of weak organic acids, a clay mineral and a water soluble, slightly acid salt. Once again, no activation of the clay mineral is disclosed.
U.S. Pat. Nos. 4,949,672 and 5,176,108 disclose litter materials based on bentonite, which are impregnated with a liquid carrier containing a bactericidal boron compound and an alkaline hydroxide. No activation of the bentonite by kneading is described.
There are also bentonite-based litter materials, as disclosed in U.S. Pat. Nos. 5,000,115, 4,657,881 and 5,000,115, for example, which have certain advantages over the organic litters. Through their ability to swell with aqueous liquids, the bentonites are capable of forming clumps. Because of this clumping, the portion of the litter wetted by the fluid can be removed separately, thus economizing on litter. The special structure of the bentonites is also responsible for their ability to adsorb unpleasant odors produced by the animal's excretions and excrement. Disposal of bentonites, furthermore, is not a burden on the environment.
According to the above-mentioned state of the art, sodium bentonites or mixtures of sodium bentonites and calcium bentonites are used as sorbents, e.g., litter material for pets. These sorbents can be used in granulated form.
However, sodium bentonites are only available in certain regions and for this reason they are usually employed only for special applications, e.g., as binder for foundry mold sand and as thickening and thixotropic agent for aqueous media. High-quality calcium bentonites can be activated for these purposes, although large quantities of alkaline activation agents (e.g., at least 3.5% sodium carbonate, in terms of the dry clay) are required in order to achieve the requisite binding ability. On the other hand, there are large quantities of calcium bentonites which are not suitable for these special applications, even after an alkaline activation, due to the low content of the primary mineral - montmorillonite.
Therefore an object of the invention is to supply these formerly unusable bentonites with low montmorillonite content, occasionally thrown away as wastes, for an economic and ecologically meaningful usage.